Build Observatory as part of runtime

runtime/observatory/test/test_helper.dart

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 library test_helper;
 
 import 'dart:async';
 import 'dart:convert';
 import 'dart:io';
 import 'package:unittest/unittest.dart';
@@ skipping 84 matching lines @@
     process.launch().then((port) {
       String addr = 'ws://localhost:$port/ws';
       new WebSocketVM(new WebSocketVMTarget(addr)).get('vm')
           .then((VM vm) => vm.isolates.first.load())
           .then((Isolate isolate) =>
               Future.forEach(tests, (test) => test(isolate)))
           .then((_) => exit(0));
     });
   }
 }